[llvm] 38ecd61 - [TableGen] Fix invalid comparison function `SizeOrder` in `getMatchingSubClassWithSubRegs`

[Matt Arsenault via llvm-commits]

Author: Ta-Wei Tu
Date: 2020-09-15T15:48:43-04:00
New Revision: 38ecd6161993ea9632efe0c0bf304bf6c2dee98f

URL: https://github.com/llvm/llvm-project/commit/38ecd6161993ea9632efe0c0bf304bf6c2dee98f
DIFF: https://github.com/llvm/llvm-project/commit/38ecd6161993ea9632efe0c0bf304bf6c2dee98f.diff

LOG: [TableGen] Fix invalid comparison function `SizeOrder` in `getMatchingSubClassWithSubRegs`

Building LLVM with -DEXPENSIVE_CHECKS fails with the following error
message with libstdc++ in debug mode:

Error: comparison doesn't meet irreflexive requirements,
assert(!(a < a)).

The patch fixes the comparison function SizeOrder by returning false
when comparing two equal items.

Added: 
    

Modified: 
    llvm/utils/TableGen/CodeGenRegisters.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/utils/TableGen/CodeGenRegisters.cpp b/llvm/utils/TableGen/CodeGenRegisters.cpp
index eeb715dded43..18a2de18c3e9 100644
--- a/llvm/utils/TableGen/CodeGenRegisters.cpp
+++ b/llvm/utils/TableGen/CodeGenRegisters.cpp
@@ -999,6 +999,8 @@ CodeGenRegisterClass::getMatchingSubClassWithSubRegs(
                       const CodeGenRegisterClass *B) {
     // If there are multiple, identical register classes, prefer the original
     // register class.
+    if (A == B)
+      return false;
     if (A->getMembers().size() == B->getMembers().size())
       return A == this;
     return A->getMembers().size() > B->getMembers().size();